diff --git a/tests/bug-2659-audit-open-crash.test.cjs b/tests/bug-2659-audit-open-crash.test.cjs
new file mode 100644
index 00000000..9f90ebda
--- /dev/null
+++ b/tests/bug-2659-audit-open-crash.test.cjs
@@ -0,0 +1,73 @@
+'use strict';
+
+/**
+ * Regression test for #2659.
+ *
+ * The `audit-open` dispatch case in bin/gsd-tools.cjs previously called bare
+ * `output(...)` on both the --json and text branches. `output` is never in
+ * local scope — the entire core module is imported as `const core`, so every
+ * other case uses `core.output(...)`. The bare calls therefore crashed with
+ * `ReferenceError: output is not defined` the moment `audit-open` ran.
+ *
+ * This test runs both invocations against a minimal temp project and asserts
+ * they exit successfully with non-empty stdout. It fails with the
+ * ReferenceError on any revision that still has the bare `output(...)` calls.
+ */
+
+const { test, describe, beforeEach, afterEach } = require('node:test');
+const assert = require('node:assert/strict');
+
+const { runGsdTools, createTempProject, cleanup } = require('./helpers.cjs');
+
+describe('audit-open — does not crash with ReferenceError (#2659)', () => {
+  let tmpDir;
+
+  beforeEach(() => {
+    tmpDir = createTempProject('gsd-bug-2659-');
+  });
+
+  afterEach(() => {
+    cleanup(tmpDir);
+  });
+
+  test('audit-open (text output) succeeds and produces stdout', () => {
+    const result = runGsdTools('audit-open', tmpDir);
+    assert.ok(
+      result.success,
+      `audit-open must not crash. stderr: ${result.error}`
+    );
+    assert.ok(
+      !/ReferenceError.*output is not defined/.test(result.error || ''),
+      `audit-open must not throw ReferenceError. stderr: ${result.error}`
+    );
+    assert.ok(
+      result.output && result.output.length > 0,
+      'audit-open must write a non-empty report to stdout'
+    );
+  });
+
+  test('audit-open --json succeeds and produces stdout', () => {
+    const result = runGsdTools(['audit-open', '--json'], tmpDir);
+    assert.ok(
+      result.success,
+      `audit-open --json must not crash. stderr: ${result.error}`
+    );
+    assert.ok(
+      !/ReferenceError.*output is not defined/.test(result.error || ''),
+      `audit-open --json must not throw ReferenceError. stderr: ${result.error}`
+    );
+    assert.ok(
+      result.output && result.output.length > 0,
+      'audit-open --json must write output to stdout'
+    );
+    let parsed;
+    assert.doesNotThrow(
+      () => { parsed = JSON.parse(result.output); },
+      'audit-open --json must emit valid JSON'
+    );
+    assert.ok(
+      parsed !== null && typeof parsed === 'object',
+      'audit-open --json must emit a JSON object or array'
+    );
+  });
+});